1. Field of the Invention
This invention relates generally to electromagnetic radiation shielding panels, such as windows or insulated glass units (IGU), useful for shielding against electromagnetic eavesdropping.
2. Technical Considerations
Electromagnetic radiation of various frequencies is produced from many sources, such as computer equipment, radio equipment, communications devices, telephones, and wireless networks, just to name a few. If this electromagnetic radiation were to be intercepted, it could be analyzed and the underlying data obtained. In order to prevent such interception, these devices can be kept in protected, e.g., shielded, rooms and great care is be taken to prevent the passage of such radiation outside of the protected area in which the equipment is located. This is particularly true in the case of confidential or classified information. While building walls typically do an adequate job of containing this radiation, conventional building windows are known to permit such radiation to escape.
In the past, it has been known to place metallic or polymeric foils over the windows to reduce radiation loss. While this does solve the problem of radiation loss, it reduces or eliminates the natural sunlight entering the building and prevents the building occupants from looking out of the windows. This can have a demoralizing effect on the occupants and makes the workplace itself less appealing.
Solar control coatings are known which affect the transmission of solar radiation through a window. These solar control coatings are typically highly transparent to visible light and are designed to reduce the passage of solar infrared energy into the building to prevent heat build-up in the building while still allowing the occupants to look out through the window. While these solar control coatings work well to control solar radiation entering the building through a window, they have, to date, not been adequate to prevent the escape of electromagnetic radiation from computers and other equipment out of the window.
Therefore, it would be desirable to provide a coating and/or coated article that could be used not only to provide solar control properties while maintaining a desirable visible light transmission but that also provide electromagnetic shielding properties.